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Apart from the benefits emulation also knows a couple of drawbacks on technical, organisational and legal aspects.

h3. Building an emulator is difficult

To be able to recreate the original computer environment in software an emulator is required. As the emulator should mimic the behaviour of that environment as accurate as possible it requires a lot of effort to develop it. To do so, not only development skills are required, but also reference material explaining the inner workings of hardware components such as CPU, memory and graphics. Luckily, many specification documents are available on the internet as well as existing open source implementations of other emulators. Accuracy has to be carefully tested of course.

h3. Original software required

Apart from the emulator, software is needed that complete the stacked chain of hardware, operating system and applications. Nowadays, software from early computer time can be hard to find. Furthermore, compiling a solid computer environment also require device drivers, codecs, fonts and other plug-ins.

h3. Understanding the old environment

Even if a particular computer environment is rendered via emulation and technically working correctly, it still requires knowledge of that particular computer era to operate with the applications and virtual hardware. The user should understand how to navigate through folders if there is no Windows Explorer or mouse support. Or which function key to hit when you want to exist an application using MS DOS. Sufficient user manuals and tutorials might be required to enable future users to operate and understand ancient computer environments.

h3. Licenses and patents

Hardware is often protected by patents and software via licenses. Emulation should not violate these protections. This can become challenging when patents on certain hardware are still in force or if a license is required for software that is already out-of-support for a long time. The European project [KEEP|] is currently undertaking a study into the legal aspects of emulation and software preservation. In September 2010 the results will become available.